The overall thrust of this research initiative is to develop new and improved means for manipulating and interrogating macro-molecular ions with strong emphasis on polypeptide species, including peptides derived from enzymatic or chemical digestion, whole proteins, and protein complexes. The ultimate objective is to maximize the structural information that can be derived from proteins and protein complexes of interest for the purpose of their identification and characterization. The work involves emphases in ion formation, ion chemistry, and instrumentation pertinent to mass spectrometry and tandem mass spectrometry. Gas-phase ions serve as surrogates for the condensed-phase species of interest. Structural information in tandem mass spectrometry is derived both from ion chemistry and the accurate measurement of the masses of the charged reaction products. The nature of the ion (e.g., protonated molecule versus radical cation) plays a major role in its chemistry, as do the reaction conditions. This research is based on the premise that new ion chemistries, new tools, and new methodologies can address many of the current limitations in the ability of mass spectrometry to derive structural information from large polypeptide species. It is also based on the premise that it is both desirable and possible to separate the ionization process from the ion manipulation/interrogation and mass analysis steps so that each can be optimized individually. To further increase the protein structural information accessible from mass spectrometry and tandem mass spectrometry, we propose the following specific aims: Specific Aim 1: New and improved ion chemistry-based approaches for protein identification and structural characterization. Specific Aim 2: New instrumentation and methodologies for tandem mass spectrometry of peptides and proteins in "hybrid" tandem mass spectrometers. Specific Aim 3: Development of novel approaches for tandem mass spectrometry of proteins ionized via matrix-assisted laser desorption ionization (MALDI). These aims will be met by the development of novel ion/ion reactions for ion transformation, an expanded range of ion activation methods, instrument development to support the new ion chemistries, and the development of new approaches to protein identification/characterization that are enabled by the advances in ion chemistry and instrumentation. PUBLIC HEALTH RELEVANCE: This project is directed at improved protein identification/characterization. The ability to identify a protein and to characterize its post-translational modifications (i.e., identities and locations of modifications) underlie much of fundamental biomedical research. This capability is also key to the identification of protein biomarkers and their correlation with disease. This project seeks to address this task by greatly expanding the information content accessible via mass spectrometry.